Individuals fed radioactive fish from water contaminated with nuclear waste.

Not science fiction, it is science fact - ordinary Americans used repeatedly as human guinea pigs in radiation experiments of the atomic age.

Over the last month, federal officials and news organizations have disclosed details of these and dozens of other studies, beginning in the 1940s and continuing into the 1970s. Hundreds of people were exposed to radiation, sometimes in doses or under circumstances that would be considered inappropriate - even inhumane - today.

The revelations have triggered a round of national soul-searching as medical ethicists, government leaders and the public at large question how such experiments could have ever been sanctioned, even in an era of Cold War uncertainty.

Despite the recent clamor, much of the research at the center of the debate has been available to the public since 1986.

A congressional subcommittee report released that year outlined 31 questionable experiments in which hundreds of Americans were exposed to radiation.

The report - "American Nuclear Guinea Pigs: Three Decades of Radiation Experiments on U.S. Citizens" - fell largely on deaf ears. The Reagan administration downplayed the importance of the report and never acted on its recommendation that the government compensate victims of improper research.

The report also received scant attention in the news media.

"Back in 1986 when I released the report, it was a different environment," says Rep. Edward J. Markey (D., Mass.), who chaired the subcommittee. "The difference now is that the Cold War is over and our government is finally willing to be honest about what it did to its own citizens in the name of national security."

In contrast to 1986, the current administration has responded by opening its files on the excesses of the past. And in doing so it has done much to keep alive the public debate over the issue.

"What I've been told about these experiments . . . leaves me appalled, shocked and deeply saddened," Energy Secretary Hazel O'Leary has said, pledging to declassify reams of documents showing government participation in tests of the Cold War era, and calling for victims of improper testing to be compensated.

O'Leary has appointed a panel of doctors, scientists and ethicists to look into a growing list of experiments that critics have called indefensible. President Clinton has ordered military and aeronautic archives combed for reports of similar studies. A federal hotline for people who think they were misused in federally supported radiation research was inaugurated two weeks ago and is swamped with up to 10,000 calls a day. Officials say it could take years to investigate every claim.

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With four decades of hindsight, it can be hard to fathom how any rationale could have been given for the most extreme of the experiments. Still, the climate of the times remains, in large part, the key to understanding what took place.

"Under the rubric of anti-communism" scientists justified all kinds of research, according to Daniel Burnstein, president of the Center for Atomic Radiation Studies. That was especially true if a study offered data on the biological effects of radiation at a time when military superiority was paramount and engineers contemplated such innovations as nuclear-powered rockets and high-speed bombers, Burnstein said.

Often experiments were designed to find the safe limits of radiation exposure.

An experiment conducted at Los Alamos Scientific Laboratory in the 1960s is a case in point. The experiment was to assess the hazards to the public from atmospheric re-entry and breakup of rockets propelled by nuclear reactors, producing particles small enough to be inhaled or ingested. So 57 workers at the lab were fed very small spheres containing radioactive uranium and

manganese to determine how long it would take the material to pass through the intestinal tract. The human guinea pigs included the wife of the principal investigator.

In the 1960s that may have seemed reasonable to those who conducted the tests, but the public perception of such tests continues to evolve.

"It's not the revelation about the existence of the studies that is different today," said Arthur Caplan, director of the Center for Bioethics at the University of Minnesota. "It's a shift in public thinking about the ethics."

That might explain why an experiment that was detailed in Markey's 1986 report has received much more scrutiny since it was the focus of a recent series of articles in the Albuquerque Tribune.

In the study conducted between 1945 and 1947, 18 severely ill patients, ranging in age from 5 to 45, were injected with plutonium to see how the highly radioactive element reacts in the human body. Patients were not informed they had been injected with plutonium until 1974. The last of them died, at age 80, in 1991.

Some scientists have praised the research, saying there is no evidence it did harm to the patients while it contributed important data that help protect thousands of workers at nuclear facilities. Critics, however, have called it unethical.

Atomic Energy Commission investigators who looked into the study concluded that truly informed consent could not have been granted in the initial phase of the experiment because even the word plutonium was classified at the time.

Another experiment under fire on ethical grounds was performed in 1949 on retarded teenagers at the Walter E. Fernald State School in Massachusetts. The students were served cereal laced with radioactive milk to monitor absorption of food.

Scientists from Harvard University and the Massachusetts Institute of Technology conducted the research in collaboration with the Quaker Oats Co.

Although parents were asked to give their consent, they were never informed the experiment involved radiation. They were told only that their children would receive a "special diet" rich in iron and vitamins, and that blood tests would be administered. The students were told they had been chosen to participate in a "science club."

Although the doses of radiation were small and probably not harmful, critics fault the experiment for seeming to prey on a vulnerable population.

Harsher criticism is reserved for experiments that intentionally caused harm. Several instances are documented in the Markey report.

In one, performed in 1946 and 1947 at the University of Rochester, six patients with normal kidneys were injected with increasing doses of uranium

salt to determine what level would produce renal injury.

Another instance concerns 130 prison inmates in Oregon and Washington state who were irradiated repeatedly on the testicles between 1963 and 1971 to measure the effects of ionizing radiation on human fertility. Because of the possibility of genetic damage, the men, who apparently gave informed consent, had to agree to undergo vasectomies.

The experiments were terminated in 1969 after a Human Subjects Review Board at the University of Washington, which participated in the experiment, refused to authorize further irradiation of inmates.

Although widespread attention to his report's findings has been late in coming, Markey said he was "glad these victims still might have some relief," a reference to the monetary compensation O'Leary has called for Congress to authorize.

As the government grapples with the good and the bad of its nuclear legacy, it may have to weigh "the difference between a harm and a wrong," said Caplan, the ethicist, and editor of When Medicine Went Mad, a book about Nazi experiments and the Holocaust.

"A harm is when you cause someone physical or mental damage, risk their dying or impose disability or dysfunction on them," said Caplan. "A wrong is when you fail to respect someone's dignity, self-determination or privacy.

"I think the kids at the Fernald School were wronged," he said. "I'm not sure that they were harmed. I take both very seriously. But lumping all the experiments together is a bit of a distortion."